Doxorubicin cardiotoxicity: diastolic cardiac myocyte dysfunction as a result of impaired calcium handling in isolated cardiac myocytes

We examined intracellular calcium transients of isolated single cardiac myocytes from rats with doxorubicin (DOX)-induced cardiomyopathy with simultaneous measurement of cell motion. DOX was administered i.p. to Sprague-Dawley rats at 2.5 mg/kg once a week for 10 weeks. Field-stimulated calcium transients and simultaneous cell motion in single myocytes were measured in the presence or absence of isoproterenol using fura-2/AM. Histopathologic examination revealed slight changes. The time courses of both calcium transients and cell motion were significantly prolonged by DOX. There was a slight but not significant reduction in parameters of contractility in both calcium transients and cell motion. The beta-adrenoceptor responsiveness of both calcium transients and cell motion was not significantly impaired compared with the controls. Our data indicated that, despite the slight histologic changes in the heart in DOX-induced cardiomyopathy, impaired sequestration of intracellular free calcium ions in individual myocytes may be one factor leading to diastolic dysfunction. Monitoring of diastolic function is important to detect early cardiotoxicity caused by DOX.

Serological studies on porcine Pneumocystis carinii pneumonia: kinetics of the antibody titers in swine herds and the association of porcine reproductive and respiratory syndrome virus infection

Serological titers to Pneumocystis carinii (Pc) and porcine reproductive and respiratory syndrome virus (PRRSV) were measured on a herd with epidemic Pc pneumonia (case herd) and two comparison herds, by an indirect fluorescent-antibody technique. In the case herd, the geometric mean titer (GMT) for Pc were 1:80 in pigs 1 week old, 1:10 in pigs 5 weeks old, and 1:80 to 1:190 in pigs over 6 weeks old. GMTs for PRRSV were > 1:145 in most of age groups over 7 weeks old. In comparison herds, Pc and PRRSV antibody titers were low in weanling pigs. The results clarified the kinetics of antibodies to Pc and concurrent infection of PRRSV in the case herd.

An angiotensin-converting enzyme inhibitor protects against doxorubicin-induced impairment of calcium handling in neonatal rat cardiac myocytes

1. The effects of doxorubicin (DOX) on intracellular calcium transients were examined in neonatal rat cultured cardiac myocytes, as were the cardioprotective effects of an angiotensin-converting enzyme (ACE) inhibitor on DOX-induced impairment of calcium handling. 2. Cultured cardiac myocytes isolated from neonatal Wistar-Kyoto rats were treated with DOX for 24 h. Field-stimulated calcium transients in single myocytes were measured in the presence or in the absence of isoproterenol using fura-2/AM. Calcium transients were also measured after the addition of DOX to myocytes pretreated with M-I (an active metabolite of delapril HCL, an ACE inhibitor. 3. Doxorubicin reduced the amplitude and maximum velocity of increase and decrease of calcium transients, prolonged the time-course of calcium transients and impaired the beta-adrenoceptor responsiveness of calcium transients in a dose-dependent manner. The DOX-induced impairment of calcium transients and beta-adrenoceptor responsiveness was improved by M-I. 4. Doxorubicin impaired both the mobilization and sequestration of intracellular calcium ions in contraction-relaxation cycles and the response of calcium transients to beta-adrenoceptor stimulation. The ACE inhibitor ameliorated DOX-induced impairment of calcium dynamics, suggesting ihat M-I, an active metabolite of delapril, protects against DOX-induced abnormal calcium handling leading to cardiac dysfunction.

Pneumocystis carinii cysts are susceptible to inactivation by chemical disinfectants

The inactivation efficacy of eight disinfectants commonly used in laboratories and animal rooms to inactive Pneumocystis carinii cysts was estimated by experimental infection in C.B-17-scid mice. The disinfectants examined in this study were 70% ethyl alcohol, 10% iodoform, 0.5% hypochlorous acid, two 1% quanternary ammonium salts, 3% hydrogen peroxide, sodium chlorite and 1% cresol soap. The lung homogenates from P. carinii infected C.B-17-scid mice were treated with each disinfectant for 15 min at room temperature, washed with saline, and inoculated into C.B-17-scid mice. Eight weeks after inoculation, lungs from these mice were examined by staining with toluidine blue O to detect P. carinii cysts. PCR amplifying 346 bp of P. carinii specific mitochondrial ribosomal RNA large segments was also performed using DNA extracted from the lungs of the mice. As a result, seven disinfectants, excepting for 0.5% hypochlorous acid, were effective in the inactivation of P. carinii cysts. These results suggest that P. carinii cysts were sensitive to chemical disinfectants even though they have been commonly considered as insensitive.

The roles of preB cell receptor in early B cell development and its signal transduction

The preB cell receptor is expressed for a short period after mu heavy chain is produced, that is, at the large preB cell stage in B cell development. The severe impairment of B cell differentiation observed in mice deficient for the preB cell receptor clearly demonstrated the importance of the preB cell receptor in B cell development. Analyses of bone marrow precursor B cells in normal and B cell-deficient mutant mice indicated the preB cell receptor transduced signals to drive cell cycle and to induce allelic exclusion. The proliferation of the preB cell receptor-expressing cells leads to the selective expansion of cells which have succeeded in the productive rearrangement of mu heavy chain gene. This process builds up a preB cell pool large enough to generate sufficient numbers of mature B cells. The preB cell receptor appears to induce allelic exclusion by shutting off the expression of recombinase activation gene (RAG). In order to analyse the signal transduction pathway downstream of the preB cell receptor, we have developed a new system in which cross-linking of Ig beta expressed on bone marrow proB cells mimics the signalling through the preB cell receptor to induce differentiation from proB to small preB cells.

Establishment of human granulocyte-macrophage colony stimulating factor producing transgenic SCID mice

Previous work has shown the usefulness of severe combined immunodeficient (SCID) mice as in vivo models for the growth of normal human haemopoietic cells and leukaemic cells. Many approaches have been made to improve the engraftment of human haemopoietic cells in SCID mice. We established transgenic mice producing human granulocyte-macrophage colony stimulating factor (hGM-CSF) with the homozygote of the scid gene. Endogenous serum hGM-CSF levels were detected by ELISA [mean 9585 pg/ml (line A, n = 4); mean 1610 pg/ml (line B, n = 4)]. Expression of hGM-CSF was observed in all organs tested including the heart, lung, liver, kidney, spleen, thymus, bone marrow and brain of hGM-CSF transgenic (hGMTg) mice. Morphological analysis of organs and peripheral blood cell counts showed no differences between hGMTg mice and their littermates. Murine Ba/F3 cells expressing functional hGM-CSF alpha beta receptor (BAF/alpha beta cells) could be successfully engrafted in hGMTg SCID mice. The cells invaded multiple organs and caused death within a few weeks of transplantation, although they infiltrated only the spleen of their littermates. These results showed that these hGM-CSF-producing SCID mice are useful as an in vivo assay system for investigating leukaemogenesis.

Establishment and characterization of transgenic mice expressing human platelet glycoprotein Ib alpha

The platelet glycoprotein (GP) Ib/IX/V is a hetero-oligomeric receptor complex for von Willebrand factor (vWF) and mediates platelet adhesion and aggregation under high shear stress conditions. It is composed of alpha and beta chain of GP Ib, GP IX, AND and GP V. To establish transgenic mice carrying human GP Ib alpha, we injected into mouse zygotes a 6 kb DNA fragment containing human GP Ib alpha gene that included entire coding sequence and putative promoter region. One hundred and thirteen offsprings were screened, and only one was found to express human GP Ib alpha protein and has passed the human GP Ib alpha gene as well as the expression of the gene to next generation. The expression of human GP Ib alpha in transgenic mice was limited to platelets and megakaryocytes. Glycocalicin, a proteolytic fragment of human GP Ib alpha found in normal human plasma, was not detected in transgenic mouse plasma. Human vWF in the presence of ristocetin supported agglutination of transgenic mouse platelets, but not of control mouse platelets.

Effects of ACE inhibition and beta-blockade on collagen remodelling in the heart of Bio 14.6 hamsters

1. The effects of angiotensin converting enzyme (ACE) inhibition and beta-blockade on collagen in the heart and on plasma catecholamines and tissue angiotensin (Ang) I and II were examined in Bio 14.6 Syrian hamsters. Male hamsters (76-79 days old) were given low-dose enalapril (3 mg/kg per day), high-dose enalapril (30 mg/kg per day), atenolol (50 mg/kg per day) or vehicle for 65 days. Age and sex matched healthy F1b hamsters were used as controls. Collagen concentration was determined by measuring hydroxyproline content and the relative proportion of type I, III, and V collagens was obtained by non-interrupted sodium dodecyl polyacrylamide gel electrophoresis (SDS-PAGE). Per cent collagen area (PCA) was measured by pixel counting in myocardial tissue by a personal computer. 2. Although heartweight (HW) and bodyweight (BW) in F1b controls were significantly higher compared with drug-treated groups and vehicles, the HW/BW ratio in cardiomyopathic Bio 14.6 hamsters tended to be high compared with F1b controls and was decreased by each drug treatment. 3. Collagen concentration, total collagen content and PCA in the heart of Bio 14.6 hamsters were significantly higher than F1b controls. Collagen concentration and total collagen content were significantly decreased in all drug-treated groups compared with vehicles. 4. The proportion of type I collagen tended to decrease while that of type III collagen tended to increase in all drug-treated groups compared with vehicles. Type V collagen in vehicle-treated group was significantly higher than in F1b controls, while it tended to decrease in all drug-treated groups compared with vehicles. 5. Plasma concentrations of catecholamines (adrenaline and noradrenaline) were decreased significantly by atenolol and high-dose enalapril, but not by low-dose enalapril. Tissue AngI remained unaltered in any of the drug-treated hamsters. Tissue AngII was decreased by the high-dose enalapril and beta-blockade, and tended to be decreased by low-dose enalapril treatment. 6. These results reveal that enalapril and atenolol produced similar beneficial effects on collagen remodelling in Bio 14.6 hamsters by decreasing the total amount of collagen, and also by changing collagen phenotypes through the inhibition of the renin-angiotensin system. Both drugs also improved myocardial morphological integrity.

Endothelin induced collagen remodeling in experimental pulmonary hypertension

To investigate pathophysiological roles of endothelin-1 (ET-1) in collagen remodeling in pulmonary hypertension, we measured: (a) mRNA expression, concentration, localization of ET-1; (b) changes in types and content of collagen in the lung; (c) and confirmed direct effects of ET-1 on type V collagen metabolism in vascular smooth muscle cells. Monocrotaline-treated rats showed pulmonary hypertension with medial hypertrophy and perivascular fibrosis of pulmonary arteries. At the progressive stage of pulmonary hypertension, both ET-1 levels and its mRNA expression in the lung increased. Total collagen in the lung rose markedly with a higher rate of increase in type V collagen. ET-1, which exists in vascular smooth muscle cells, other perivascular cells and endothelium, stimulated type V collagen production. Our results suggest that local production of ET-1 in the lung contributes to progression of pulmonary hypertension through changes in phenotypes and content of collagen.

Comparative study and cDNA cloning of the flavoprotein subunit of mitochondrial complex II (succinate-ubiquinone oxidoreductase: fumarate reductase) from the dog heartworm, Dirofilaria immitis

Mitochondrial complex II functions as a fumarate reductase (FRD), the reverse reaction of succinate dehydrogenase (SDH), and plays an important role in the anaerobic respiratory chain of parasitic helminths. In this study, complex II from the dog heartworm, Dirofilaria immitis adult, which is thought to act as a homolactatic fermenter, was examined in terms of its enzymatic features and primary structure in order to investigate the possible role of mitochondria in this filaria. Mitochondria from D. immitis adult showed high FRD activity when the enzymatic assay was performed using methylviologen as an artificial electron donor. The ratio of SDH to FRD in D. immitis was comparable to that in Ascaris suum adult, which is known to have an anaerobic mitochondrial respiratory chain with a high FRD activity of complex II. The FRD activity of D. immitis mitochondria was inhibited by the sulfhydryl reagent N-ethylmaleimide (NEM), while that of A. suum complex II was resistant to this inhibitor. The presence of the flavoprotein (Fp) subunit, which contains the substrate binding active site, was confirmed in D. immitis mitochondria by immunoblotting using a monoclonal antibody against the A. suum Fp subunit. By homology probing with the polymerase chain reaction, the entire cDNA for the D. immitis adult Fp was cloned and sequenced. The deduced amino acid sequence showed significant homology to that of A. suum and other mitochondrial Fps, in contrast to much less similarity to bacterial FRD, even though the D. immitis complex II showed high FRD activity. These results are the first indication of the presence of a functional complex II in D. immitis mitochondria.

Direct effects of angiotensin I, angiotensin II, an ACE inhibitor and a serine proteinase inhibitor on cultured heart cells from spontaneously hypertensive rats

1. The purpose of the present study was to investigate how angiotensin I (AI), angiotensin II (AII), an angiotensin converting enzyme inhibitor (ACE inhibitor; ACE-I) and a serine proteinase inhibitor contribute to the protein metabolism of cultured newborn spontaneously hypertensive rats (SHR) heart cells. We examined the uptake of [3H]-uridine and [3H]-proline into cultured cardiac myocytes and fibroblasts, respectively. 2. Both AI and AII increased the uptake of [3H]-uridine into myocytes in a concentration-dependent manner. However, the effect of AI was denied in the presence of the ACE-I with the concentration of 10(-6) g/mL. Both AI and AII increased the uptake of [3H]-proline into cardiac fibroblasts in a concentration-dependent manner. However, this effect was only partially abolished in the presence of 10(-6) g/mL of the ACE-I, which was the maximal concentration that did not exert any effect on the [3H]-proline uptake. In the presence of AII receptor antagonist, [Sar1, Leu8]-AII, the uptake of [3H]-proline into cardiac fibroblasts was completely inhibited. Moreover, the stimulatory effects of AI on the uptake of [3H]-proline into cardiac fibroblasts were completely inhibited in the presence of a serine proteinase inhibitor in addition to the ACE-I. 3. These results suggest that an ACE-I has different effects on protein metabolism in the heart and also suggest the presence of serine proteinase in cultured cardiac fibroblasts from SHR.

Stage-specific isoforms of complex II (succinate-ubiquinone oxidoreductase) in mitochondria from the parasitic nematode, Ascaris suum

Complex II from mitochondria of the adult parasitic nematode, Ascaris suum, exhibits high fumarate reductase activity and plays a key role in the anaerobic electron transport observed in these organelles. In contrast, mitochondria isolated from free living second stage larvae (L2) of A. suum show much lower fumarate reductase activity than those from adults, whereas succinate dehydrogenase activities of mitochondria in both stages are comparable. In the present study, biochemical and antigenic properties of the partially purified enzymes from both larval and adult mitochondria were compared. Larval complex II eluted from the DEAE-Cellulofine column chromatography at a lower salt concentration than adult enzyme, whereas the apparent molecular size of both enzyme complexes estimated by gel permeation column chromatography was the same. The fumarate reductase activity of larval complex II was less than 3% of that of adult enzyme, and the Km values for substrates were significantly different between the two complexes. The flavoprotein subunit of larval complex II could be distinguished from that of adult complex II by two-dimensional gel electrophoresis and peptide mapping. The antibody against the smallest subunit (small subunit of cytochrome b558) of the adult enzyme did not cross-react with that of the larval enzyme. These results suggest that larval complex II differs from adult enzyme and is more similar to aerobic mammalian enzymes with low fumarate reductase activity. This is the first direct indication of the two different stage-specific forms of mitochondrial complex II.

Calcium transients in single myocytes and membranous ultrastructures during the development of cardiac hypertrophy and heart failure in rats

1. We examined changes in intracellular calcium transients of separated single myocytes from the right ventricle (RV) of the rat heart during the change from adaptation to maladaptation in response to a pressure overload. 2. Right ventricular hypertrophy (RVH) secondary to pulmonary hypertension was induced by a subcutaneous injection of monocrotaline. Developed tensions of the RV-free wall were decreased as RVH progressed. Single myocytes were separated from the RV during different stages of RVH. Fura-2/AM-loaded cells were field stimulated, and changes in calcium transients were measured by Olympus OSP-3 system. We also examined membranous ultrastructures (sarcoplasmic reticulum, mitochondria, surface caveolae) involved in calcium metabolism in the hearts using scanning electron microscopy. 3. We observed characteristic changes in calcium transients during the change from adaptation to maladaptation, and also found that one parameter (amplitude) of calcium transients appeared to be correlated with the changes in the number of sarcoplasmic reticulum. 4. These results provided some insights into the mechanism of calcium handling of hypertrophied heart in response to a pressure overload from adaptation to maladaptation especially when stimulatory frequency was high, and suggested that heart rate control is a very important factor for the treatment of patients with congestive heart failure.

Contrasting effects of isoproterenol and phosphodiesterase III inhibitor on intracellular calcium transients in cardiac myocytes from failing hearts

1. Effects of a newly developed phosphodiesterase (PDE) III inhibitor, E-1020, on intracellular calcium transients were compared with those of isoproterenol (ISO) in isolated single myocytes from failing hearts secondary to pulmonary hypertension induced by monocrotaline injection. Myocytes were isolated by enzyme digestion using a Langendorff apparatus. Changes in intracellular calcium concentrations ([Ca2+]i) were recorded using a fura-2 fluorescence microscopic technique. Cyclic AMP contents of the hearts were measured by radio-immunoassay. 2. Myocytes from failing hearts showed Ca2+ transients with a low peak (low amplitude) and delayed decline of Ca2+ transients. Both ISO and E-1020 increased peak [Ca2+]i, max + d[Ca2+]i/dt, and max - d[Ca2+]i/dt in a concentration-dependent manner while both agents decreased T80L (time to 80% decline of amplitude from peak light). The concentrations which increased peak [Ca2+]i by 50% were 1.6 x 10(-9) mol/L of ISO and 2 x 10(-6) mol/L of E-1020. These concentrations increased cAMP in the heart to the same levels. Analysis of the effects of both agents on peak [Ca2+]i versus max - d[Ca2+]i/dt showed that ISO is much more effective on peak [Ca2+]i while E-1020 is more effective on max - d[Ca2+]i/dt. 3. These results showed that the effects of ISO and E-1020 on the parameters of intracellular Ca2+ transients of single myocytes from failing hearts are slightly different, and suggest that E-1020 may improve diastolic function as well as systolic function in failing hearts.

Sequence comparison between the flavoprotein subunit of the fumarate reductase (complex II) of the anaerobic parasitic nematode, Ascaris suum and the succinate dehydrogenase of the aerobic, free-living nematode, Caenorhabditis elegans

Complex II in adult mitochondria of the parasitic nematode, Ascaris suum, exhibits high fumarate reductase activity and plays a key role in the anaerobic electron-transport observed in these organelles. In the present study, cDNAs for the flavoprotein (Fp) subunits of complex II have been isolated, cloned and sequenced from both A. suum and the aerobic, free-living nematode, Caenorhabditis elegans. Additional sequence at the 3' end of the mRNAs was determined by the Rapid Amplification of cDNA Ends (RACE). Nucleotide sequence analysis of the A. suum cDNAs revealed a 22-nucleotide trans-spliced leader sequence characteristic of many nematode mRNAs, an open reading frame of 1935 nucleotides and a 3' untranslated region of 616 nucleotides including a poly (A) tail from a polyadenylation signal (AATAAA). The open reading frame encoded a 645 amino acid sequence, including a 30 amino acid mitochondrial presequence. The amino acid sequences for the Fp subunits from both organisms were very similar, even though the ascarid enzyme functions physiologically as a fumarate reductase and the C. elegans enzyme a succinate dehydrogenase. The ascarid sequence was much less similar to the Escherichia coli fumarate reductase. The sensitivity of other Fp subunits to sulfhydryl reagents appears to reside in a cysteine immediately preceding a conserved arginine in the putative active site. In both nematode sequences, this cysteine is replaced by serine even though the succinate dehydrogenase activity of both enzymes is still sensitive to sulfhydryl inhibition. A cysteine six residues upstream of the serine may be involved in the sulfhydryl sensitivity of the nematode enzymes. Surprisingly, in contrast to succinate dehydrogenase activity, the fumarate reductase activity of the ascarid enzyme was not sensitive to sulfhydryl inhibition, suggesting that the mechanism of the two reactions involves separate catalytic processes.

Different effects of an angiotensin converting enzyme inhibitor and a calcium antagonist on protein metabolism in rats with right ventricular hypertrophy

OBJECTIVE

We examined the effects of a calcium antagonist and an angiotensin converting enzyme (ACE) inhibitor on contractile and non-contractile protein metabolism and cardiac function in a monocrotaline-induced right ventricular hypertrophy model, in order to define the effects of these drugs on cardiac hypertrophy.

METHODS

One week after monocrotaline injection, male Sprague-Dawley rats were given either a calcium antagonist (nilvadipine; 3 mg/kg per day) or an ACE inhibitor (delapril-HCl; 30 mg/kg per day) for 2 weeks. Right ventricular pressure, the right ventricle: (left ventricle + interventricular septum) ratio, myosin isoenzymes, collagen concentration, collagen types and contractility of right ventricular free wall were examined.

RESULTS

In untreated rats significant monocrotaline-induced right ventricular hypertrophy with an increase in the proportion of collagen types III and V was observed. There were no significant changes in collagen concentration. Both drugs reduced right ventricular pressure to the same degree and decreased right ventricular hypertrophy. However, the inhibitory effect of delapril on right ventricular hypertrophy was stronger than that of nilvadipine. Nilvadipine reduced the collagen concentration and reversed changes in collagen types, whereas delapril did not have any significant effect on collagen concentration or collagen types. Cardiac contractility was improved by delapril, but not by nilvadipine.

CONCLUSIONS

The results show that a calcium antagonist disproportionately inhibited contractile and non-contractile protein metabolism, whereas an ACE inhibitor proportionally inhibited them and improved cardiac function in a model of right ventricular hypertrophy. The improvement in cardiac function may be due partly to the proportional inhibition of contractile and non-contractile proteins elicited by an ACE inhibitor.

Contrasting effects of an angiotensin converting enzyme inhibitor and a calcium antagonist on calcium transients in isolated rat cardiac myocytes

OBJECTIVE

The aim was to examine the effects of an angiotensin converting enzyme (ACE) inhibitor and a calcium antagonist on intracellular calcium transients in isolated cardiac myocytes from a monocrotaline induced right ventricular hypertrophy model.

METHODS

One week after monocrotaline injection, Sprague-Dawley rats were given either an ACE inhibitor (delapril-HCl) or a calcium antagonist (nilvadipine) for two weeks. Using fura-2/AM, calcium transients were measured in single myocytes separated from the right ventricle.

RESULTS

The severe right ventricular hypertrophy observed in untreated rats was significantly reduced in drug treated animals. The inhibitory effects of delapril were more prominent than those of nilvadipine, although both drugs reduced right ventricular pressure to the same extent. Calcium transients in delapril treated rats were similar to those in control rats. On the other hand, the calcium transient in nilvadipine treated rats was decreased and its time course was prolonged. The changes were similar to those found in monocrotaline treated rats. The responsiveness of calcium transients to isoprenaline in delapril treated rats was similar to that in control rats. The responsiveness in nilvadipine treated rats was decreased, and was similar to that in monocrotaline treated rats. Delapril improved developed tension and the beta adrenoreceptor responsiveness of developed tension to isoprenaline.

CONCLUSIONS

Although delapril and nilvadipine inhibited cardiac hypertrophy in monocrotaline treated rats, significant improvement of contractile function and beta adrenoreceptor responsiveness was observed only in the delapril treated rats. This improvement was partially due to the improvement in calcium transients and the restoration of the beta adrenoreceptor responsiveness of the calcium transient to beta adrenergic stimulation.

Three new reduced anthracycline related compounds from pathogenic Nocardia brasiliensis

Three new metabolites were isolated from a pathogenic bacterium, Nocardia brasiliensis IFM 0075 strain, a producer of a new anthracycline antibiotic (SO-075R1) and its mutant strain (IFM 0075-13-1). The structural studies showed that they are reduced anthracyline related compounds. Some biosynthetic routes of these metabolites were discussed.

Human complex II (succinate-ubiquinone oxidoreductase): cDNA cloning of the flavoprotein (Fp) subunit of liver mitochondria

Complex II (succinate-ubiquinone oxidoreductase) is an important enzyme complex in both the tricarboxylic acid cycle, and the aerobic respiratory chains of mitochondria in eukaryotic cells and prokaryotic organisms. In this study, homology probing with mixed primers for the polymerase chain reaction and subsequent sequence analysis were successfully applied to clone cDNA for the flavoprotein (Fp) subunit of human liver complex II. The isolated clone contains an open reading frame of 1,992 nucleotides and encodes a mature protein of 621 amino acids with a molecular weight of 68,011. The amino acid sequence was highly homologous with that of bovine heart Fp (93.2%) and was quite different from the partial sequence of human placental Fp reported previously [Malcovati et al. (1991) in Flavins and Flavoproteins 1990, pp. 727-730], which showed striking homology to that of Bacillus subtilis. To solve this discrepancy, the partial cDNA sequences of the stomach and placental Fp subunits of human complex II were determined in addition to the full length cDNA of liver. The sequence data, sensitivity to thiol reagents and antigenic properties indicated that the major from of FP subunit in human complex II is unique at least among the three tissues analyzed, and is more similar to the Fp subunit of bovine heart than to that of B. subtilis.

Prominent inhibitory effects of tranilast on migration and proliferation of and collagen synthesis by vascular smooth muscle cells

To obtain some ideas about prevention of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we examined the effects of transilast (anti-allergic agent) on migration and proliferation of, and collagen synthesis by, cultured vascular smooth muscle cells (VSMC) from the thoracic aorta of WKY rats. Tranilast was added to culture medium containing 10% fetal calf serum (FCS). The cultures were pulse-labeled with 3H-thymidine (TdR) or 3H-proline (Pro). TdR and Pro uptake into VSMC were measured. The effect of tranilast on migration of VSMC was examined by using culture dishes of an original design. We also examined the inhibitory effects of various drugs, such as a Ca antagonist, an angiotensin converting enzyme (ACE) inhibitor, a phosphodiesterase inhibitor, elastase, colchicine, and mitomycin C, on proliferation and migration of VSMC. Our data showed that the inhibitory effects of tranilast on migration and proliferation of, and collagen synthesis by, VSMC were prominent. Maximal percentage inhibition of proliferation, migration and collagen synthesis was 60.8 +/- 2.3%, 52.7 +/- 14.7% and 62.1 +/- 8.1%, respectively. On the other hand, the inhibitory effects of other drugs, with the exception of colchicine and mitomycin C, on proliferation and/or migration of VSMC were not very strong. Although the inhibitory effects of colchicine and mitomycin C were strong in vitro, their clinical usefulness may be limited by systemic side-effects. These results indicate the potential usefulness of tranilast for prevention of restenosis of coronary arteries after PTCA.

[Contrast echocardiographic detection of pulmonary arteriovenous shunt in a hypoxemic patient with liver cirrhosis]

A 62-year-old man with liver cirrhosis and hypoxemia was admitted to evaluate the etiology of hypoxemia. The patient had noticed exertional dyspnea for three years. Physical examination, laboratory tests, ultrasonography and liver scintigraphy revealed liver cirrhosis. The arterial blood gas test showed hypoxemia (PO2 46.3 mmHg). Chest roentgenogram showed old pulmonary tuberculosis and the pulmonary function test demonstrated decreased FEV 1.0% and %DLco, which did not account for the marked hypoxemia. Contrast echocardiography was performed by injecting hand-agitated saline into the antecubital vein. Three seconds after the right ventricle was opacified, the contrast echoes appeared in the left atrium and then the left ventricle. Pulmonary arteriography revealed no pulmonary arteriovenous fistula. Hemodynamic data showed low pulmonary vascular resistance. Contrast echocardiography by injecting hand-agitated saline from the catheter tip was performed at both pulmonary arteries and the left atrium was opacified by each injection. The hypoxemia was mainly attributed to a intrapulmonary arteriovenous shunt. Although the etiology of hypoxemia in liver cirrhosis seems to be multifactorial, the intrapulmonary arteriovenous shunt is the most important factor. Contrast echocardiography was useful for detecting this shunt.

Gou-teng (from Uncaria rhynchophylla Miquel)-induced endothelium-dependent and -independent relaxations in the isolated rat aorta

Gou-teng is a drug used for treatment of hypertension in Chinese medicine. Its antihypertensive action has been previously confirmed in the spontaneously hypertensive rat (SHR). Here, its vasorelaxing effect and the mechanisms of actions were studied in vitro. Gou-teng extract (GTE) relaxed the norepinephrine (NE)-precontracted aortic ring preparations isolated from Wistar Kyoto rats (WKY) with and without intact endothelium; the latter was significantly less sensitive than the former. The GTE-induced endothelium-dependent relaxation was significantly inhibited by NG-monomethyl-L-arginine (NMMA) in a dose-dependent manner while indomethacin did not affect the relaxation. Atropine inhibited the acetylcholine (ACh)-induced endothelium-dependent relaxation but did not the GTE-induced one. Furthermore, once GTE was applied, the following NE-induced contraction was significantly reduced even after repeated washout. NMMA effectively reduced and rather reversed this residual effect of GTE. From these results, it is concluded that GTE relaxes the NE-precontracted rat aorta through endothelium-dependent and, to lesser extent, -independent mechanisms. The endothelium-dependent component would be mediated by EDRF/NO pathway in which the muscarinic cholinoceptors were not involved. Thus, GTE appears to be a potent and long-lasting vasodilator mainly through EDRF/NO release.